Write C# method to find number of vowel character in the given sentence

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace vowel_count
{
    class Program
    {
        static void Main(string[] args)
        {
            char[] str = new char[10];
            Console.WriteLine("enter a string(Max 10 char):");
            str = Console.ReadLine().ToCharArray();
            int i = 0;
            int vowels=0;
            for (i = 0; i < str.Length; i++) 
            {
                if (str[i] == 'A' || str[i] == 'E' || str[i] == 'I' || str[i] == 'O' || str[i] == 'U' ||
                    str[i] == 'a' || str[i] == 'e' || str[i] == 'i' || str[i] == 'o' || str[i] == 'u')
                {
                    vowels++;         
                }
            }
                Console.WriteLine("the number of vowels {0}", vowels);
                Console.ReadKey();
            }
        }
}